Decentralized biometric authentication platform

ABSTRACT

A biometric authentication platform (10) uses fault-tolerant distributed computing to determine if a supplied biometric sample and a sample stored in a registry are from the same person. A collection of reference samples is maintained in a distributed ledger (115) with immutable history of modifications. Results of matching are stored in a separate distributed ledger (125) providing an immutable history log. Coordinated use of both ledgers (115, 125) enable biometric authentication of registered users (140) in real time. Users (140) may interact with providers (150) and/or trusted circles of other users in order to recover user records from the user ledger (115).

TECHNICAL FIELD

The present disclosure relates in general to biometric authentication,and in particular to a decentralized platform for biometricauthentication.

BACKGROUND

Biometric authentication is increasingly utilized as a mechanism forconfirming an individual's identity in connection with varying types oftransactions. For example, in recent years, smartphones have begunutilizing fingerprint sensors and/or facial recognition as biometricmeans of authenticating a user for, e.g., access to a device, access toconfidential information stored within a device, or authorization of atransaction such as a purchase transaction.

However, conventional frameworks for biometric authentication may havenumerous limitations. For example, typically, at least one entityinvolved in an authentication transaction must be a trusted party. Suchplatforms may be more vulnerable to code hacking, and suffer from a lackof auditability thus impairing trustworthiness. Matching biometricsamples with templates is typically performed on a centralized serverwhich lacks transparency and is prone to machine failure and adversaryattacks. Biometric templates used for authentication and matchingresults are typically not recorded in immutable form, and therefore areof limited value in proving authenticity if a dispute arises. Whilebiometric templates may be sensitive personal information belonging totheir owners, in many biometric systems, users do not have authority tocontrol access to their own biometric templates, including removal ofaccess for stolen templates and template replacement.

For these and other reasons, the challenge of providing a scalableplatform for biometric authentication with little or no centralizationor trust requirement has been largely unmet.

SUMMARY

In accordance with some aspects described herein, a biometricauthentication platform may use fault-tolerant distributed computing todetermine if a supplied biometric sample and a sample stored in aregistry are from the same person. Collection of reference samples ismaintained in a distributed user ledger that may provide immutablehistory of modifications. Results of matching are stored in a separatedistributed authentication ledger that may also provide an immutablehistory log. Coordinated use of both ledgers allows biometricauthentication of registered users in real time. An immutable historylog serves as a proof of authenticity and non-repudiation for externaltransactions that triggered biometric authentication by the platform.

In some embodiments, biometric authentication confirms the identity ofan individual to validate a transaction with another entity. This otherentity can be a person or a business such as a bank or hospital. Theto-be-verified individual may be referred to herein as a User, and theother entity may be referred to as a Provider.

To register with the platform, a User may capture a biometric sample andupload it to the user ledger, such as via a transaction director. Atauthentication time, the User captures another biometric sample andsends it (e.g. via the transaction director) for matching with thepreviously recorded sample. The sample captured during registration maybe referred to as a Template, and the sample captured duringauthentication may be referred to as a Live Scan.

A biometric authentication platform may be built on top of twoindependent distributed ledgers. One ledger is used to store Templatesalong with related user-specific data. This ledger is referred to hereinas UL for “user ledger”. The second ledger can be used to storeauthentication transaction records. Each time the platform receives arequest to biometrically authenticate a registered user, biometricmatching of Live Scan to Template may be carried out and the outcome maybe saved as a transaction record in this ledger. This matching processis referred to herein as Authentication and the ledger may be called ALfor “authentication ledger”.

In some embodiments, with the exception of new User registrations, allrequests handled by the platform may involve both ledgers. Processingflow sequencing is orchestrated by the transaction director or TD forshort. Apart from coordination and sequencing of steps executed on ULand AL, TD software module also serves as a gateway connecting bothledgers to the outside world.

The AL and UL are logical representations. They can be implemented usingthe same physical networks or two physical networks that are completelyseparate from one another, by sharing nodes, or one network may becontained within the other.

Each ledger is preferably maintained by a network of interconnectednodes. Each of the AL nodes maintains a local copy of the entire AL.Each of the UL nodes also maintains a copy of the entire UL. Some of thetransactions on the UL require access to the logs stored in the AL. Thisaccess is provided by either collocation of a pair of UL and AL nodes(e.g. attached to a transaction director) or by a network bridge betweenthem.

These and other aspects of the systems and methods described herein willbecome apparent in light of the further description provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic block diagram of a platform for biometricauthentication.

FIG. 2 is a user record diagram.

FIG. 3 is a UL record with provider account attributes.

FIG. 4 is a set of Trusted List attributes.

FIG. 5 is a schematic block diagram of an AL node network with multipleprocessing clusters.

FIG. 6 is a user authentication request.

FIG. 7 is an authentication ledger record.

FIG. 8 is a process for validation of a user request.

FIG. 9 is a process for an authentication protocol.

FIG. 10 is a process for validation of a provider request.

FIG. 11 is a process for adding a provider to a user ledger record.

FIG. 12 is a process for user authentication requested by a provider.

FIG. 13 is a process for trusted provider initiation of a user recordrecovery.

FIG. 14 is a process for user registration of a new device duringtrusted provider user record recovery.

FIG. 15 is a process for completing a trusted provider user recordrecovery.

FIG. 16 is a process for removing providers from a user record providerlist.

FIG. 17 is a process for adding a registered device to a user record.

FIG. 18 is a process for creating a list of trustees.

FIG. 19 is a process for inviting a trustee to join a trustee list.

FIG. 20 is a process for initiating a trusted circle recovery of a userrecord.

FIG. 21 is a process for a trustee receiving a request to confirm auser.

FIG. 22 is a process for applying a scrambling technique within abiometric authentication platform.

FIG. 23 is a user ledger record portion enabling application of ascrambling technique.

FIG. 24 is schematic illustration illustrating insertion of test tasksto prove authenticity of matching results.

DETAILED DESCRIPTION OF THE DRAWINGS

While this invention is susceptible to embodiment in many differentforms, there are shown in the drawings and will be described in detailherein several specific embodiments, with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention to enable any person skilled in the art tomake and use the invention, and is not intended to limit the inventionto the embodiments illustrated.

Systems and methods are described which may include one or morecharacteristics that are highly beneficial for usability and marketadoption of a biometric authentication platform. Such a platform willpreferably have high availability, with the ability to maintain a highthroughput regardless of total transaction volume. For example, maximumthroughput may be limited wholly or primarily by total processing poweravailable within a computing network. Network size may be dynamicallyadjusted to maintain consistent responsiveness. Such a platform is alsopreferably fault tolerant and designed to withstand multiple concurrentnode failures. In some embodiments, a level of fault tolerance may becontrolled in a network configuration.

Embodiments are also preferably wholly or highly decentralized andwithout a single point of failure. Such a platform may be deployed in atrustless environment without a governing body or any other authorityparticipant. Platforms may be architected to assure data integrity andease of auditing, by maintaining an immutable log of transactions. Forbiometric authentication, this enables the use of transaction records asa proof of authenticity. For a user registry, this facilitates dataprovenance inquiries and record history tracking. Platforms describedherein may also protect confidentiality of biometric data, leveragingencryption and programmatically enforcing controlled data access. Suchplatforms may also be highly configurable and support installationsranging from a globally accessible public network, to a high-securityisolated environment on a smaller scale.

FIG. 1 is a schematic block diagram illustrating a platform 10 forbiometric authentication, in accordance with a first embodiment. Theauthentication platform 10 includes transaction director (TD) 100, ULnode network 110 implementing distributed User Ledger (“UL”) 115, and ALnode network 120 implementing distributed Authentication Ledger (“AL”)125. As described further hereinbelow, UL 115 may further run one ormore smart contracts 115A; AL 125 may run one or more biometric matchingalgorithms 125A to reach decentralized consensus. TD 100 includes, or isattached to (e.g. functionally, logically, or via physical or equipmentcollocation) at least one node from each of node networks 110 and 120(i.e. attached UL node 110A and attached AL node 120A). TD 100 furtherincludes or interacts with web interface 130. Web interface 130 providesa programmatic mechanism for network-based interactions between TD 100and: a personal electronic device (PED) 145 utilized by User 140; andmanagement console 155 associated with Provider 150.

In many embodiments, a user may use one or more trusted personalelectronic devices 145 in order to interact with the transactiondirector or provider. Modern personal electronic devices may beparticularly convenient, having fingerprint scanning or advanced imagingcapabilities that may be utilized for capturing biometric samples.However, while the user device is illustrated in the embodiment of FIG.1 as a personal electronic device, a User's registered device need notbe so limited. It is contemplated and understood that a user 140 mayutilize any computing device capable of network communications andinteraction with the user, in place of PED 145. For example, a bank mayrequire a customer (acting as a User) to authenticate himself or herselfon site at the bank's premises using a computing device owned by thebank, such as an ATM machine. In such a use case, the device private keycan be stored in a private database maintained by the bank andtransferred to the ATM or computing device through its internal networkduring authentication. Similarly, it is understood that Providermanagement console 155 may be implemented using any of a variety ofnetwork-enabled computing devices.

In general, requests handled by biometric authentication platform 10 maybe divided into two broad categories. Transactions resulting in thechanged state of the UL 115 fall into a first category. New userregistration, appending some relevant data fields to an already existinguser record, disabling a record, etc. are all examples of suchtransactions. Transactions of this kind are typically not time criticalby nature and can take seconds to execute without having a detrimentaleffect on the user experience. Transactions of a second category areAuthentications logged in AL 125. These transactions typically requirelow latency and may be essential to the perceived responsiveness andoverall usability of the platform.

Updates of UL 115 modify User records and should be authorized. Thisauthorization should be carried out prior to execution of anyledger-changing transactions, other than new user registrations. Aprocess of authorization can involve Template retrieval followed byAuthentication. Upon successful Authentication, a UL 115-modifyingtransaction may be authorized and allowed to proceed.

The Transaction Director

One or more transaction directors may be included in embodiments of asystem for biometric authentication. A transaction director (“TD”) canplay two roles: (1) the TD acts as a gateway, allowing Users 140 andProviders 150 to access data content and request services from UL 115and AL 125; and (2) the TD coordinates step-by-step execution ofrequests received from Users 140 and Providers 150.

Thus, TD 100 implements a thin gateway for interactions amongst UL 115,AL 125, User 140 and Provider 150. As a gateway, TD 100 exposes APIsthat can be called by client software such as a Web server,business-layer custom components, or the like.

As a transaction coordinator, TD 100 receives requests originated byProviders 150 or Users 140, and handles them following prescribedexecution paths, including validation steps, UL queries, UL smartcontract invocations, and Authentication Protocol invocations on AL 125.

While TD 100 may be considered centralized in terms of managing messagesamongst other resources, TD 100 does not itself affect the authenticityof records stored in the UL 115 and AL 125, because UL 115 and AL 125are only updated when consensus is made over a decentralized network(e.g. amongst UL nodes 110 and AL nodes 120, respectively). Further, insome embodiments, multiple instances of TD 100 may be implemented, eachwith attached UL and AL nodes, and preferably having an associated webinterface 130. If, for example, a particular TD 100 is untrusted or atransaction party wishes to verify a TD's operation, a User 140 andProvider 150 can read back transaction records from a different TD (ormultiple different TDs) immediately after a transaction occurs, in orderto verify the transaction. Additionally or alternatively, a transactionparticipant may audit transaction records (and/or audit TD operation) atany time after a transaction is completed, by reading back transactiondata from one or more TDs other than the one via which the transactionwas orchestrated.

Attached UL node 110A maintains a copy of the UL 115 locally for TD 100.Similarly, attached AL node 120A maintains a copy of AL 125 locally forTD 100. Despite the fact that TD 100 has access to both ledgers viaattached nodes 110A and 120A, TD 100 is incapable of directly modifyingcontents of either one of them.

TD 100 preferably need not implement business logic, but is ratherstateless. TD 100 need not keep track of the state of the externalprotocols it is executing. Intermediate protocol-state-specific dataused in some scenarios may be stored inside the affected UL record. Thisway, a large number of Users 140 and Providers 150 can interact viamultiple instances of TD 100 concurrently, even when they are connectedto the same UL 115 and AL 125. Handling of incoming service requests toTD 100 may be accomplished, and audited, in real time.

In general, TD 100 can orchestrate the following sequence of steps:

(1) Template retrieval. TD 100 requests a template from the local ULnode 110A and gets an immediate response.

(2) Authentication of Template against Live Scan. TD 100 sends aTemplate and Live Scan to one or more Processor servers amongst AL nodes120 (preferably Processor servers optimized for biometric matching). TheProcessor servers produce a result, returning it to TD 100. TheProcessor servers also add a record of the transaction to the AL 125.The duration of this step two hinges on the performance of thesespecialized servers.

(3) Execution of a transaction modifying UL 115 upon successfulauthorization in step (2). Execution of this transaction may beaccomplished using a standard path of a smart contract. The transactionmay be executed and validated in parallel on multiple instances withinAL nodes 120. Process of validation may include a step where priorauthorization from step (2) has to be verified. This verification is aquery by a UL validating node 110 into the AL 125. This query can onlyproduce a result after the AL 125 addition from step (2) has had enoughtime to propagate through the network of AL nodes 120. Once this happensand the query returns a result, smart contract processing can proceed,affecting the UL change that is eventually replicated across the entirenetwork of UL nodes 110.

Operations within step (3) may take more time than those of steps (1)and (2). But, as it was stated earlier, transactions that include step(3) are typically not time critical. The significant majority ofrequests expected to be handled by the platform, in some embodiments,are initiated by Providers needing to confirm a User's identity. Suchrequests generate new AL records but do not affect the UL and,therefore, may be processed in steps (1) and (2) above, but need notproceed to step (3), whereby the platform may be capable of meeting highthroughput requirements.

The User Ledger (UL)

User ledger (UL) 115 is a collection of user records. Each recordcorresponds to a registered User and stores a User's Template. UL 115 ispreferably implemented using Distributed Ledger Technology. UL 115 ishosted on a network of interconnected computing devices, namely, ULnodes 110. Each node 110 preferably stores an identical copy of UL 115.UL 115 preferably leverages a number of key properties offered by theunderlying technology, such as: byzantine fault tolerance; modificationsto UL 115 are controlled by a distributed consensus protocol; UL 115 isdecentralized (no central authority) except scenarios when it's deployedon a private network controlled by a single entity; UL 115 maintains animmutable history log, such that it is always possible to audit UL 115and recreate its earlier state all the way back to UL's genesis; and alluser data stored in the ledger is either encrypted or hashed, with thetemplate possibly being scrambled using techniques described furtherhereinbelow.

The state of UL 115 is modified by submitting transactions to smartcontracts executing on the ledger. History of transactions is persistedin the immutable log. Every time the state of UL 115 changes, it has topropagate through the entire network of nodes 110 storing a full replicaof the ledger. This step causes latency. On the other hand, when clientsoftware, such as TD 100, reads data from UL 115, this process runslocally on a node 110A handling the request and may thus be executedwith minimal latency.

FIG. 2 illustrates a typical ledger structure that may be utilized whena new User record is added to UL 115. The first field 200 is ULID—aunique identifier assigned to the record. This identifier may be a hashof a human-readable text supplied by the user. By default, users arepreferably prompted to use their e-mail address but the system mayaccept any alphanumeric string as long as it results in a unique hash.The second field 210 is Template from the biometric sample supplied byUser at registration. The contents of the first two fields may be fixedand never change after record creation.

The third field 220 reflects a current state of the user registration.Initially it is set to “ACTIVE”, but it can also be set to “DISABLED” or“RECOVERY”. In addition to the status setting this field may alsocontain some service information when a record is in RECOVERY. Whenstatus is set to ACTIVE, a service information portion of the field 220may be empty.

The fourth field 230 is a nonce. Initially, it's set to zero. Every timea state of the record is changed by a smart contract, this field 230 ispreferably incremented. The purpose of field 230 is to protect UL 115from replay attacks.

The fifth field 240 contains information about the device used atregistration. Other than new user registration, to be able to interactwith UL 115, users must use one of their previously-registered devices.Registered devices can be mobile devices (such as a smartphone ortablet), or other electronic devices owned by the user. In someembodiments, a User may also utilize a shared device, or even a publicterminal such as a bank automated teller machine (ATM), as a registereddevice, as long as the User trusts that device to be safe for storingprivate data including cryptographic keys used by the platform.

The fifth field 240 is an example of a UL record attribute. Even thougha UL record must have at least one registered device attribute, anynumber of additional attributes can be appended to a record. Moregenerally, three types of attributes may be attached to a record withinUL 115: Registered Device, Provider Account, and Trusted List.

FIG. 3 illustrates an exemplary set of UL record attributes with twoRegistered Devices and three Provider Accounts. (UL record ULID,Template, Status and Nonce fields are not shown in FIG. 3 .)

A Registered Device attribute to a record within UL 115 (such asAttributes 300A and 300B in FIG. 3 ) may store information about devicesthat are authorized to produce Live Scans. A Registered Device attributemay consist of two fields: (1) a hash 302A-B of a hardware identifierfor the device, such as an IMEI (which field may also be referred to asa Device ID); and (2) a public key 304A-B corresponding to the privatekey stored locally on a device referred to as PuK-Dev (described furtherbelow).

A Provider Account attribute stores information authorizing and enablingsecure transactions between a User and particular Providers. ExemplaryProvider Account attributes 310A, 310B and 310C are illustrated in FIG.3 . The User has registered three Providers: “Gold Gym acct #123”(associated with Provider Attribute 310A), “Loyalty Program acct #456”(associated with Provider Attribute 310B), “Chase Bank checking”(associated with Provider Attribute 310C). Chase Bank is “Trusted” (asindicated in field 312C) meaning that it is authorized to be used in arecord access recovery protocol. Each Provider stores its private key(PrK-Prov1, PrK-Prov2 and PrK-Prov3) in an external database maintainedby the respective Provider.

The Provider Account attribute may be constructed using a cryptographicpublic/private key pair. The Private Key is typically stored in adatabase maintained by a Provider associated with the attribute, and isnever shared on UL 115.

In practice, a Provider Account Attribute such as attribute 310A mayinclude four fields: a Provider ID 311, a Trusted Flag 312, encryptedaccount information 313, and a Public Key Translation Table 314. AProvider ID 311 may be formed from a hash of a public key for theProvider associated with the Attribute. Preferably, Provider IDs onlyexist in the context of a single User record, i.e., the same Providerwill have different IDs for different Users. The Trusted flag 312 may beset to YES to indicate authorization for the Provider associated withthe Provider Account Attribute to assist the User associated with the ULentry to assist in recovery of a UL record. Recovery procedures wouldtypically be used when a User loses access to or control of allregistered devices associated with a UL record. The encrypted accountinformation field 313 is a description of the provider and/or of theaccount in free format. Text contents within encrypted accountinformation field 313 is preferably encrypted using the Provider privatekey.

Public Key Translation Table 314 provides a cryptographic link enablingRegistered Devices and Trusted Providers to recover a public key for auser, without storing the user's public key openly in UL 115. Inparticular, each Provider maintains a unique public key associated bythe Provider with a specific User. This unique, user-specific public keymay be referred to as PuK-ULID. PuK-ULID can be used to decryptidentifiable information about the Provider with which it is associated.To preserve confidentiality, the PuK-ULID is not openly stored in UL115. Instead, PuK-ULID is preferably encrypted using a PuK-Devassociated with a registered device. Thus, a table row within Public KeyTranslation Table 314 for Provider 1 (i.e. Provider Attribute 310A) maycontain a key-value pair of: Device 1 ID: E_(PuK_Dev1) (PuK-Prov1);where the key is the ID of Device 1, and the value is the public key ofProvider 1 encrypted with the public key of Device 1. To reverse thisdouble encryption of user public key PuK-ULID, a Registered Device orTrusted Provider looks up its associated entry in translation table 314,retrieves the encrypted public key, and decrypts the user's PuK-ULIDusing its own local private key.

Since each registered device has its own PuK-Dev, multiple encryptedPuK-ULIDs are stored in a UL record; one for each registered device.Thus, in the example of FIG. 3 , the User has registered two devicesidentified by hashes of their respective IMEIs: Device 1 ID and Device 2ID. Private keys (PrK-Dev1, PrK-Dev2) are stored on the devices. Theirrespective public keys (PuK-Dev1 and PuK-Dev2) are stored in the secondfield of the attributes.

Trusted List Attribute

FIG. 4 illustrates Trusted List attributes 400A and 400B. Trusted Listattributes 400A, 400B may be appended to a UL record and used in aTrusted Circle record recovery protocol as an alternative to recoverywith the help of a Trusted Provider. Trusted List refers to a variablelength list of users (Trustees) who can participate in a voting processto confirm identity of a User who lost all registered devices. There maybe multiple Trusted Lists in one UL record (e.g. lists associated withattributes 400A and 400B, in the embodiment of FIG. 4 ). The sameTrustee may appear in multiple Trusted Lists of a single UL record.

A Trusted List attribute 400 may be configured using a Registered Device(e.g. Device 1 associated with UL record field 300A and Device 2associated with UL record field 300B). The Trusted List attribute 400contains four fields: (1) a unique List ID 401, which may beautomatically generated when the List attribute is created, as a hash ofthe data object with three fields (e.g. ULID, Device ID, hash of thelist of trustee IDs); (2) an array of key-value pairs 402, with one pairper each Registered Device; the key is set to a Registered Device ID andthe value is a description of the Trusted List encrypted with the devicepublic key; (3) a minimum number of required votes 403; preferably, theUser can set this number to be less than or equal to the total number ofTrustees in the list; and (4) a List of Trustees 404. The List ofTrustees 404 is a variable length array of key-value pairs. The key is aULID of a Trustee. The value is Trustee's status. When a Trustee isfirst added to a Trustee List, the status is set to PENDING. After aTrustee confirms his or her participation, the Trustee's status changesto CONFIRMED. When a record recovery is in progress and Trustee respondswith a vote, the Trustee's status changes to VOTED. Thus, for example,Trusted List attribute 400A is associated with two registered devices402, has a list description of “Family members”, requires at least twovotes for recovery (specified in field 403), and includes a list ofthree Trustees in total (ULID_(MOM), ULID_(DAD), ULID_(Mary)). TrustedList attribute 400B is also associated with the user's two registereddevices, has a list description of “Coworkers”, requires at least fourvotes for recovery, and includes a list of four Trustees in total.

The Authentication Ledger

Authentication Ledger is a collection of records that stores details ofprocessed User Authentication requests. FIG. 5 provides a schematicblock diagram illustrating AL nodes 120, implementing AL 125.

AL 125 is implemented using Distributed Ledger Technology. It is hostedon a network 120 of interconnected computing devices called nodes. Nodes520 host AL 125 and interact with one another, and will Processors 510,to maintain AL 125. Processors 510 are nodes that also host specializedsoftware responsible for the execution of biometric matching processingalgorithms. Latency of Authentication request execution typicallydepends on the efficiency with which Processors 510 handle theircomputational tasks. Processors 510 should be implemented on hardwarethat is optimized for and capable of the biometric matching computationsfor which they will be used. In addition to processing Authenticationrequests, Processors 510 are responsible for storing the full logs ofAuthentication requests processed by them.

Some characteristics of AL 125 are defined by the selection of theunderlying Distributed Ledger Technology platform and its configuration.For example, preferably AL 125 is: crash-fault-tolerant, unlessinstalled on an insecure network where it may bebyzantine-fault-tolerant; decentralized (no central authority) exceptscenarios where it's deployed on a private network controlled by asingle entity; scalable to maintain required throughput; and immutable.Other preferred characteristics and benefits are domain-specific, forexample: AL 125 maintains low latency using optimized hardware forbiometric matching; and AL 125 supports real time audits. The size of AL125 is optimized and transaction privacy is improved through the use ofexternal storage for biometric data; to preserve auditability, AL 125records store hashes of biometric data. Full logs of processed UserAuthentication requests are preferably stored externally. Further, AL125 supports full biometric privacy mode where externally stored logsare encrypted.

FIG. 6 illustrates an exemplary User Authentication request 600 that maybe transmitting by a TD 100 and implemented by AL nodes 120. ALID 601 isused as a record identifier in AL 125, and is determined (preferablycomputationally) by the instance of TD 100 that is submitting therequest 600. TD 100 uses an appropriate technique for the calculation,to ensure a unique ALID for each transaction. For example, for a UserAuthentication request originated by a Provider 150, ALID 601 may becomputed by hashing a data object comprising: a User ID (ULID),transaction information such as a hash of transaction data supplied by aProvider 150 (e.g. TX hash 610), and a Provider ID (such as a hash of apublic key assigned to a User 140 by Provider 150 at Registration). Forother types of requests, an ALID may be computed by hashing a dataobject with: ULID, Device ID (such as a hash of a hardware identifierassociated with a device used in the request), and a nonce (i.e. a fieldof the User record that gets incremented each time the record isupdated).

Timestamp 602 is obtained by TD 100 from its local environment andsupplied with the request 600.

Live Scan 604 is supplied by the User 140 associated with request 600.As explained elsewhere herein, Live Scan 604 contains current biometricdata from User 140, for which a comparison is requested with a User'sTemplate. Template 606 specifies biometric information with which LiveScan 604 is to be compared. As described elsewhere herein, Template 606may be retrieved from UL 115 by Transaction Director 110.

Encrypted HASH(Live Scan) 608 is supplied by the User 140, and may beused to verify the authenticity of Live Scan 604 during auditing. Inparticular, it may be decrypted by using a public key of one of theUser's devices (PuK-Dev), and should equal the unencrypted hash of LiveScan data that is stored within the AL record, thus verifying, e.g.,that the processed Live Scan was not switched with fake biometric dataen route from the User device 145 to AL Processors 510.

TX Hash 610 provides a hash of Transaction details supplied by theProvider 150 that requested Authentication of User 140. The source ofhash 610 may be a detailed record of a transaction between a Provider150 and a User 140.

Device details 612 provides details descriptive of a device used by User140 to produce or transmit Live Scan 604. For example, a User 140 mayrespond to an authentication request with a Live Scan, whether procureddirectly by a user PED 145 (e.g. a fingerprint scan, palm print scan orfacial recognition data procured by sensors within PED 145), or procuredby another source and transmitted by PED 145. When a User 140 respondsto an authentication request with a Live Scan, software on User PED 145may include encrypted detailed information retrieved from device,potentially via a device operating system (e.g. geo-location, SIM cardinformation, IMEI, and the like) (subject to regulations and userprivacy considerations), which information may be conveyed from PED 145to transaction director 100 via, e.g., web interface 130. This field maybe used when the Provider 150 that requested User Authenticationrequires such details to, e.g., confirm information about or imposeconstraints or requirements on the Live Scan source. The data within thedevice details 612 field may be encrypted with the requesting Provider'spublic key to avoid openly storing potentially private informationconcerning User 140 on a distributed ledger. Nonetheless, inclusion oftransaction hash 610 and device details 612 in a record within AL 125enables AL 125 records to be used as a proof of authenticity andnon-repudiation for external transactions.

User MSG Hash 614 optionally includes a hash of the text message sent tothe User 140 with a description of or reason for the requestedauthentication. The message is sent from Provider 150 and displayed tothe User 140 in connection with agreement of User 140 to the requestedbiometric authentication. By performing biometric authentication, theUser 140 authorizes a transaction described in the message. After thetransaction, the full message is stored locally by User 140 and Provider150, with MSG Hash 614 stored directly in AL 125. In a future auditevent, one or both sides can present the full message and the User MSGHASH 614 can be retrieved from AL 125 and used to prove the authenticityof the presented message.

Cryptographic key 616 is optional, and includes a cryptographic key thatmay be used to encrypt the full biometric samples (Live Scan 604 andTemplate 606) supplied with the request 600, when stored locally byProcessors 510. When this feature is used, future audit will only bepossible by a party holding a key that's needed for decryption.

FIG. 7 illustrates a format for an AL record 70 stored within AL 125.ALID 702 is supplied with a request 600 in field 601. Timestamp 704 issupplied with a request 600 in field 602. Hash (Live Scan) 706 and Hash(Template) 708 are hashes of biometric samples supplied with the request600. Encrypted HASH (Live Scan) 710 is supplied with the request 600 infield 608. TX Hash 712, device details 714 and User MSG Hash 716 arealso supplied in the request 600 in fields 610, 612 and 614,respectively.

Field 718 contains the match outcome, which in some embodiments may beexpressed as a yes/no result. Cluster ID field 720 contains anidentifier for a processing cluster utilized to perform the matchingoperation yielding the result of field 718. This ID 720 can be usedduring audits for locating the original Authentication request recordwith full copies of Template and Live Scan (since that data ispreferably stored locally by the Processor 520 performing the matchingoperation).

Handling of Authentication Requests

Each Authentication request is handled by a group of Processors 510,which may be referred to as a Processing Cluster. For example, in theembodiment of FIG. 5 , AL nodes 120 include processing cluster 515Ahaving three Processors 510, and processing cluster 515B having fourProcessors 510. In actual practice, processors 510 may be allocated toprocessing clusters with an objective of achieving fault-tolerantoperation. AL 125 is built on transaction-level consensus. Processors510 within a single Processing Cluster 515A, 515B receive anAuthentication request, process it and agree on the Authenticationoutcome. This decision is final and is saved in the AL 125. If for somereason Processors 510 within a Processing Cluster 515 are unable toreach consensus (e.g. a majority of the Processors 510 within a Cluster515 fail and/or lose connectivity), the Processing Cluster 515 returns afailure result to the requestor, but wrong Authentication outcome nevergets written into AL 125.

AL nodes 120 can be set up in different environments in terms ofsecurity. The most critical components of AL nodes 120, the Processors510, may be hosted in a tightly controlled secure environment where amain concern would be an intermittent connectivity loss or some otherhardware failure rather than Processors 510 being hacked in such amanner as to control majority voting and produce false results. In thisenvironment, Processing Clusters 515A, 515B can be configured to use oneof the Crash-Fault-Tolerant distributed consensus algorithms that offerbetter performance and smaller Cluster size compared to the ByzantineFault Tolerant family of protocols. The latter are designed to deal witha public network that is likely to contain misbehaving nodes, andtherefore will require more Processors 510 in the Cluster 515 and willthus typically be slower to reach a consensus.

Additional methods and configurations may be used in setups whereProcessors 510 operate in a less secure environment. Reliability ofresults can be improved by using security auditing software that feedspreprocessed Template-Live Scan pairs to the Processors 510 and comparesthe generated results with pre-calculated values as described elsewhereherein.

Another way of monitoring security is by setting up a monitoring stationthat selectively intercepts incoming Template-Live Scan pairs, processesthem locally, and compares the result with the one produced by aProcessing Cluster 515A, 515B to which the comparison is assigned.

Processing Clusters 515 may be virtual groupings in a sense that Clustermembers 510 do not necessarily need to share the same hosting facility:physical or cloud. AL 125 is preferably designed for scalability.Whenever a lack of processing capacity becomes a performance issue, moreprocessors 510 may be added to AL nodes 120 in order to address theproblem. Processing Clusters 515 can be formed dynamically forload-balancing optimization. Distributed Processing Cluster colocationmay also be used to improve decentralization and eliminate a centralhosting authority that might otherwise be effectively imposed on AL 125if processors 510 were collocated in a single hosting facility orcommonly-controlled hosting facilities.

Except for failed consensus situations on the cluster level, each UserAuthentication request results in a record added to AL 125. Tofacilitate audits, it may be necessary to store biometric data used bythe Authentication request so that authentication matching results canbe reproduced. However, some types of biometric data that may bedesirable for use in authentication may involve significant volumes ofdata. Moreover, while each of AL nodes 120 is expected to host a fullreplica of AL 125, many AL nodes 120 may not be powerful Processorstations 510, such that storing each transaction's biometric data withinthe distributed ledger may impose significant storage burdens. To reducerequired storage capacity for AL nodes 120, in some embodiments, each ALrecord will only include the hash of the processed request, as describedabove. A full copy of the request will preferably be stored by some orall of Processors 510 on a high-capacity fault tolerant storage media.This arrangement may significantly reduce the size of AL 125 whilepreserving its full auditability.

In some embodiments, AL 125 may support a full biometric privacy mode ofoperation. In this mode, externally stored logs of User Authenticationrequests are encrypted.

Transaction Director Request Handling

Requests handled by TD 100 may fall into at least two broad categories:(1) requests from Users 140; and (2) requests from Providers 150. Notethat preferably, requests are always signed and the digital signaturesof Users 140 and Providers 150 are verified by TD 100. For simplicity,the application and verification of digital signatures may not beexplicitly listed in processes described hereinbelow.

FIG. 8 illustrates a method by which a transaction director may processa User request. This method may sometimes be referred to as Validationof a User Request. In step 805, a user 140 transmits a request to TD 100via web interface 130. Request messages sent to TD 100 by a User 140preferably include the following fields: User ID (UL record identifierULID); Device ID (Hash of the hardware identifier of the device); andRequest-specific data. The Request is signed by a User 140 with aprivate key stored locally on the user's device 145. A respective publickey is attached to the message.

In step 810, TD 100 validates the digital signature applied to theRequest. In step 815, TD 100 validates the User ID specified in theRequest. Validation in step 815 succeeds if TD 100 is able to retrievefrom UL 115 a copy of the User record identified by the ULID received instep 805. In step 820, TD 100 validates the requesting device 145 byfinding the Device ID received in step 805 amongst Registered Devices inthe User record retrieved in step 815. In step 825, TD 100 validates thepublic key supplied in step 805 by checking to confirm that it matchesthe public key of the Device ID in the User record retrieved in step815. In any of the validations in steps 810, 815, 820 or 825 fails, thenthe overall User request is deemed to have failed (step 840). However,if the validations in steps 810, 815, 820 and 825 all succeed, then theoverall validation effort is deemed successful (step 830).

In some scenarios, such as record recovery or new device validation,only one of steps 810-825 may be performed, with the remaining stepsskipped.

In a Trusted Provider recovery, the ULID check in step 815 is replacedby a Recovery Session PIN check, as explained further in connection withFIGS. 13 and 14 .

In the event that a User Request is successfully validated (step 830),TD 100 may continue processing, such as via execution of anAuthentication Protocol. FIG. 9 illustrates an exemplary AuthenticationProtocol method.

In step 900, TD 100 computes an AL record ID (“ALID”), as describedelsewhere herein. In step 905, TD 100 sends a request 600 to aProcessing Cluster (515A, 515B). The content of the request of step 905is illustrated and explained in connection with FIG. 6 .

In step 910, each of the processors 510 within a processing cluster(e.g. 515A or 515B) executes a biometric matching algorithm on Template606 and Live Scan 604, and computes a result. In some embodiments, theresult is an affirmative or negative indication that the Live Scanmatches the Template.

In step 915, each processor 510 within the selected processing cluster(515A, 515B) adds a record documenting the processed request 600, to alocal log maintained by the processor. The record added in step 915preferably includes complete copies of the Template and Live Scan usedin generating the result computed in step 910. If request 600 containeda cryptographic key 616, cryptographic key 616 is used to encrypt therecord prior to storage in step 915.

In step 920, processors 510 within the selected processing cluster(515A, 515B) seek to agree on a matching result, following rulesprescribed by a consensus protocol governing the cluster.

In step 925, the processing cluster (515A, 515B) adds a record of theAuthentication request 600 to AL 125. In the record 700 logged in AL125, the live scan content is replaced by live scan hash 706, thetemplate content is replaced by template hash 708, and cluster ID field720 is added, as described further elsewhere herein.

In step 930, the processing cluster (515A, 515B) sends the ALID andmatching or Authentication result to TD 100, reporting completion of theauthentication protocol.

Subsequent actions by TD 100 depend on the nature of the UserAuthentication request. In a case where a User Authentication isrequested by a Provider 150 that is transacting with a User 140, TD 100in turn finishes processing and returns an ALID and matching result tothe calling Provider 150. In other cases, TD 100 may proceed by callinga smart contract 115A on UL 115 supplying data present in the UserRequest. In other scenarios, TD 100 may proceed by sending notificationsto User devices, or other actions as desired to utilize theauthentication result returned in step 930.

A transaction director may also process requests from Providers 150.FIG. 10 illustrates a process for handling a message or request from aprovider 150. In step 1000, a Provider 150 transmits a Request to TD 100via web interface 130. This request may contain the following fields: aULID; a Provider ID (such as a hash of the public key that was assignedto a User 140 by a Provider 150 during Provider Registration); andrequest-specific data. Such a provider request may be signed with theprivate key held by the Provider 150. A corresponding public keycertificate may be attached to the message.

In step 1005, TD 100 verifies the validity of the Public Key Certificatecontained within the request of step 1000. In step 1010, TD 100validates a digital signature applied to the Provider Request. In step1015, TD 100 validates the ULID specified in the request of step 1000.Validation in step 1010 succeeds if TD 100 is able to retrieve a copy ofthe User record identified by the ULID within the Request from UL 115.In step 1020, TD 100 checks if the requesting Provider 150 has beenauthorized by the User 140 specified in the request. A Provider IDsupplied with the request in step 1000 has to match one of the ProviderIDs found in the User record (e.g., within a Provider attribute (310A,310B, 310C)). If TD 100 is processing a request to add a new Provider150 and the associated Provider ID is already registered, validationresults in failure (step 1030). Moreover, execution of the ProviderRequest is aborted on failure of any of the validations of steps 1005,1010, 1015 or 1020. Otherwise, presence of the Provider ID in the recordis interpreted as success (step 1040).

Addition of a Provider Account to a User Record

Preferably, to be able to request User Authentication, a Provider has tobe authorized by the User. This authorization may come in the form of aProvider Account attribute attached to the User Record, as describedelsewhere herein. Some Provider Accounts can also be designated as“Trusted” indicating that they are authorized to assist a User in recordrecovery should the User lose all of his or her Registered Devices. Insome embodiments, a user record in a database maintained by a Provider150 already has a ULID and a pair of keys created by the Provider(namely, PrK-ULID(private) and PuK-ULID(public).) Provider Accountattributes in records within UL 115 are identified by a Provider ID thatis a hash of PuK-ULID.

In this context, FIG. 11 illustrates an exemplary process for additionof a Provider Account to a User record within UL 115. In step 1100, aProvider 150 sends to TD 100 an “Add Provider” request containing a userrecord ID (ULID), PuK-ULID, and a Provider title encrypted withPrK-ULID. In step 1105, TD 100 runs a Validation of Provider Requestprotocol, as described in connection with FIG. 10 . In step 1110, usingdata from the User record retrieved by TD 100 in step 1105, TD 100 sendsnotifications to all User Registered Devices containing the Providerpublic key PuK-ULID, an encrypted title, a list of Registered DeviceAttributes, and a list of Provider Account attributes marked “Trusted”.

In step 1115, an application running on User device 145 maintains a ULIDand private/public key pair in local storage. PED 145 receives themessage from TD 100 sent in step 1110, and decrypts the public keys ofTrusted Providers from the list of Provider Account attributes. PED 145further builds a Public Key Translation Table for the new ProviderAccount attribute. PED 145 creates a new Provider ID by hashingPuK-ULID. PED 145 then sends to TD 100 an “add provider authorized”request with Live Scan data, an encrypted hash of the Live Scan, DeviceID, new Provider ID, Encrypted Title, a Trusted setting, and a PublicKey Translation Table.

In step 1120, TD 100 runs protocols for Validation of User Request (asdescribed in connection with FIG. 8 ) and Authentication (as describedin connection with FIG. 9 ). In step 1125, TD 100 forwards a full copyof data received from PED 145 (and a software application executedthereby) to a smart contract 115A running on UL 115. The smart contract115A validates the request and updates UL 115 with a new version of theUser record containing a newly added Provider Account attribute. In step1130, TD 100 receives confirmation of the transaction, relaying it tothe Provider 150.

Exemplary Provider Requests for User Authentication

In an exemplary embodiment, a customer may request a service from aservice provider. The service provider desires to confirm that theregistered customer is indeed the person requesting the service. In sucha scenario, the service provider can do so by using a biometricauthentication platform that already contains a reference biometricsample of the customer. As an added benefit, the platform may allowsaving of transaction details along with a record of the authenticationresult in an immutable log. The Provider can obtain a copy of thisrecord at will and use it as proof of the authenticity of pasttransactions.

There are a wide array of business scenarios and Provider types whereUser Authentication requests may be beneficially used. For example,banks can add and enforce biometric authentication requirements to theprocess of contactless payments. In another example, biometricauthentication can be added to online payments and replace or enhancethe popular “3-D Secure” protocol. In yet another example, biometricauthentication can be used instead of an ID card in all scenarios wherea customer registers first, and obtains a product or service later, suchas: gym membership, tickets purchased online, etc.

FIG. 12 illustrates an exemplary process for implementation of such userauthentication scenarios. In step 1200, a Provider 150 sends a “UserAuthentication Request” request to TD 100. The Request of step 1200includes ULID, Provider ID, and ENCR_(PrK-ULID)(TX hash, User MSG). TheRequest may be formed by Provider 150 by, e.g., retrieval ofUser-specific information from a Provider-maintained database, such asULID, private key assigned to the User by the Provider (PrK-ULID), and acorresponding public key (PuK-ULID). The Provider 150 puts togethertransaction details such as transaction amount, time, merchantinformation, and other information that may be relevant to a particulartransaction. A transaction hash (“TX hash”) is created by hashing thisdata together. This hash will subsequently be stored immutably in AL 125as part of the Authentication request record. Provider 150 may generatea text-based message (“User MSG”) that a User 140 will see on the user'sPED 145, such as, “This is your bank. Please confirm the charge of$500.” As described elsewhere herein, full copies of this message may beretained in the logs of the Provider application (e.g. accessible bymanagement console 155) and the user application (e.g. executed by PED145). Meanwhile, the hash of this message will be stored immutably in AL125 and can be used as proof of the content of the original message.Provider 150 uses its private key to encrypt the data pair consisting ofthe transaction hash and the text message, to produce ENCR_(PrK-ULID)(TX hash, User MSG).

In step 1205, TD 100 runs a Validation of Provider Request protocol, asdescribed in connection with FIG. 10 . In step 1210, using a User recordretrieved in step 1205, TD 100 sends notification to all RegisteredDevices (i.e. PEDs 145) attaching the Public Key Translation Tableassigned to the requesting Provider 150, and the unmodifiedENCR_(PrK-ULID) (TX hash, User MSG) from step 1200.

In step 1215, User 140 (via PED 145) responds to TD 100 with a Userauthentication response. In some embodiments, the User authenticationresponse may be formed in accordance with the following steps. Each PED145 maintains a ULID and private/public key pair in local storage. Auser application on PED 145 hashes its hardware identifier and uses itfor the Public Key Translation Table lookup. PED 145 locates acorresponding entry with the encrypted copy of the Provider public keyPuK-ULID, and decrypts it using the local private key. PED 145 usesPuK-ULID to decrypt the encrypted data pair ENCR_(PrK-ULID) (TX Hash,User MSG). PED 145 hashes PuK-ULID to produce the Provider ID. PED 145may then display the decrypted User MSG on, e.g., an associated devicescreen. This message prompts User 140 to provide a Live Scan. PED 145may also capture additional information in accordance with Providerrequirements (e.g. local time on PED 145, phone number information,geolocation of PED 145, etc.) This additional information may beencrypted with the PuK-ULID, creating ENCR_(PuK-ULID) (Auth. Detail).PED 145 hashes the User MSG. PED 145 hashes the Live Scan and encryptsthe Live Scan hash with the local private key on PED 145. PED 145 maythen send to TD 100 the “User authentication response” message withULID, Live Scan, Encrypted Hash of Live Scan, Device ID, TX hash,Provider ID, encrypted authentication details, and a hash of the UserMSG.

In step 1220, TD 100 performs a Validation of User Request protocol andan Authentication Protocol, as described in connection with FIGS. 8 and9 , respectively. Finally, in step 1225, TD 100 returns the ALID andmatching result to the requesting Provider 150.

Exemplary Use for Biometrically Authenticated Signed Documents

In some embodiments, the biometric authentication platforms andprocesses described herein may be utilized for a variety of diverseapplications. One such application is biometric authentication of signeddocuments. Transaction data that is hashed to produce a TX hash (e.g. TXhash 610, 712) may include more than just a collection of bookkeepingfields, such as “Paid to: XXX; Payee Bank: YYY; Amount paid: ###.”Instead the transaction description may contain information ofindependent significance, such as the content of a document.

For example, AL records may be used as proof of authenticity of legalcontracts, as demonstrated in the following scenario. A User 140 may bein a rental office, prepared to sign a rental agreement. The parties maysign a contract. The Rental office party to the contract may be deemed aProvider 150 and registered on UL 115. The rental office (i.e. Provider150) may scan the signed contract, and hash the digital filecorresponding to the signed contract. The hashed digital file may beused as TX hash (e.g. in fields 610 and 712). The rental office, asProvider 150, requests User Authentication, supplying a text messagewith the contract number as a User MSG. This process creates a record onAL 125 that permanently links the hash of the scanned contract to theUser's “biometric signature”. In the future, the renter (User 140) wouldnot be able to claim that its signature on the contract is forged orotherwise inauthentic. Likewise, the rental office (Provider 150) wouldnot be able to modify the content of the originally-signed paperdocument without the modification being reveals by subsequentauthentication. In this way, by hashing a scanned copy of a document asthe TX hash, authenticity of the document may be verified using systemsand methods described herein.

Record Recovery by a Trusted Provider

Should a User 140 lose all of his or her Registered Devices, Providersdesignated as “Trusted” can assist in registering a new device whicheffectively restores a User's ability to use his or her UL record withinUL 115.

FIG. 13 illustrates an exemplary process for initiating a User RecordRecovery by a Trusted Provider. In step 1300, a Provider 150 sends arequest to initate recovery (“InitiateRecoveryReq”) to TD 100. TheInitiateRecoveryReq contains a User record ID (ULID) and Provider ID. Instep 1305, TD 100 runs the Validation of Provider Request protocol. Ifsuccessful, in step 1310, TD 100 sends the ULID and Provider ID receivedin the InitiateRecoveryReq to a smart contract 115A on UL 115, which (a)changes the user record state 220 from ACTIVE to RECOVERY, and (b)creates a unique Session PIN. The Session PIN can be used in validationwhen a User 140 proceeds to add a new device. The Session PIN isintroduced in order to ensure that a Trusted Provider and User arecommunicating and verifying each other while going through the protocolsteps, as described. The Session PIN may be saved in registration statefield 220 of a UL record, as described elsewhere herein. In step 1315,the smart contract 115A on UL 115 returns the Session PIN to TD 100, andTD 100 forwards the Session PIN to Provider 150—at which point Provider150 waits for User 140 to register a new Device.

FIG. 14 illustrates a process via which User 140 may subsequentlyregister a new Device. In step 1400, Provider 150 provides User 140 withthe Session PIN returned in step 1315. The Session PIN may be provided,for example, in person, or via telephone. User 140 enters the SessionPIN in a new PED 145, and produces a Live Scan. In step 1405, User 140(e.g. via new Device PED 145) sends to TD 100 a request to add arecovery device (“AddRecoveryDeviceReq”), containing the Session PIN,Live Scan, an encrypted hash of the Live Scan, a hash of the devicehardware identification (Device ID), and the local device public key.

In step 1410, TD 100 runs Validation of User Request and Authenticationprotocols, as described elsewhere herein. In step 1415, TD 100 forwardsinformation received as a result of step 1410 to a smart contract 115Aon UL 115, which updates the User record, adding a new Registered DeviceAttribute corresponding to the new Registered Device PED 145, thuscompleting the new device registration.

However, at this point, the User's Record in UL 115 is still marked in aRECOVERY status. FIG. 15 illustrates a final phase for Record Recoveryby a Trusted Provider. In step 1500, Provider 150 sends to TD 100 arequest to get the recovered key (“GetRecoveredKey”), which includes aULID associated with the User record, and a Provider ID. In step 1505,TD 100 executes a Validation of Provider Request protocol. In step 1510,using data from the User record retrieved in step 1505, TD 100 repliesto Provider 150, sending a list of Registered Device attributes and alist of Provider Account attributes associated with the User record. Instep 1515, the Provider 150 processes the received lists, to identifythe new Registered Device and its key. Provider 150 updates the PublicKey Translation Table, adding entries encrypted with the public key ofthe new Device being added. Provider 150 then sends a “completerecovery” request to TD 100, containing the user record ULID, ProviderID, and an updated list of Provider Account Attributes. In step 1520, TD100 runs a Validation of Provider Request protocol. Finally, in step1525, TD 100 forwards a copy of data received by it in step 1515 to thesmart contract 115A on UL 115. The smart contract in turn validates therequest, updates the User record with an updated version of the list ofProvider Account Attributes, and changes the User record Status fieldfrom RECOVERY to ACTIVE.

Removing Providers from a User Record

In some circumstances, a User may wish to remove one or several ProviderAccounts from his or her record. Removed Providers will no longer beable to send User Authentication requests. FIG. 16 illustrates a processfor such removal of Provider accounts.

In step 1600, User 140 (via PED 145) sends to TD 100 a request toretrieve a provider list (“RetrieveProviderListReq”), containing a ULID,Live Scan, encrypted hash of Live Scan, Device ID, and device publickey. In step 1605, TD 100 runs Validation of User Request andAuthentication protocols, as described elsewhere herein. In step 1610,using data retrieved during step 1605, TD 100 replies to User 140 withthe list of Provider Account Attributes contained in the User record.

In step 1615, an application implemented by PED 145 of User 140 decryptsProvider descriptions contained within the Provider Account Attributesreturned in step 1610, and displays the decrypted Provider descriptionsto User 140. Using PED 145, User 140 may edit the list (includingdeleting one or more Providers from it) and save an updated version.User 140 then sends to TD 100 a request to update the Provider list(“UpdateProviderListReq”) to TD 100, containing the ULID, Live Scan,encrypted hash of Live Scan, Device ID, and the updated list of ProviderAccount attributes.

In step 1620, TD 100 runs Validation of User Request and Authenticationprotocols, as described elsewhere herein. In step 1625, TD 100 forwardsdata received in step 1615 to the smart contract 115A implemented on UL115. The smart contract validates the request and updates contents ofthe User record.

Addition of a New Registered Device to a User Record

Preferably, only registered devices can be used for serving UserAuthentication requests by Providers. A User may have any number ofRegistered Devices configured in his or her UL record. Typically, to add(i.e. register) a new device, the User must be in possession of one ofthe previously registered devices.

FIG. 17 illustrates a process via which a user may register a new deviceusing a previously-registered device. In step 1700, a User 140 installedan application on a new (i.e. not previously-registered) PED 145 (“NewDevice”), and via an application configuration process, selects anoption presented on New Device to add the New Device to an existing ULaccount. In step 1705, New Device sends to TD 100 a request to add a newdevice (“AddNewDeviceReq”) containing the User's ULID, Live Scan,encrypted hash of Live Scan, Device ID and Device public key. In step1710, TD 100 runs a Validation of User Request protocol andAuthentication protocol, as described elsewhere herein. In step 1715,using data from the User record retrieved in step 1710, TD 100 sendsnotifications to all Registered Devices associated with the User record,attaching the New Device ID, New Device PuK, and the list of ProviderAccount attributes.

In step 1720, User 140 uses one of the previously-registered Devices toreply to TD 100. In particular, an application on thepreviously-registered Device re-calculates the Provider Accountattribute list, updating the Public Key Translation Tables for the NewDevice and its public key. User 140 (via the previously-registeredDevice) then sends a request to authorize the New Device to TD 100,which request includes the ULID, Live Scan, encrypted hash of the LiveScan, old Device ID, New Device ID, old Device PuK, New Device PuK, andthe updated list of Provider Account Attributes.

In step 1725, TD 100 runs the Validation of User Request andAuthentication Protocols, as described elsewhere herein. Finally, instep 1730, TD 100 forwards data received in step 1720 to the smartcontract 115A running on UL 115. The smart contract validates therequest and updates contents of the User record with the updated versionof the Provider Account Attributes and a Registered Device attributecorresponding to the New Device.

Adding a New List of Trustees to a User Record

When a User 140 loses access to all of the Registered Devices, the Usercan no longer use services provided by various biometric authenticationplatforms described herein. Devices to be used for User Authenticationhave to be registered. To register a New Device, a User typically needsto be in possession of a previously-registered Device.

However, in some embodiments, other mechanisms may be provided foradding a New Device. One such mechanism utilizes the assistance of aProvider 150 that was previously designated by the User 140 as“Trusted”. Some Users, however, may not have such a Trusted Provider. Inthat case, a “Trusted Circle” protocol may be utilized as anothermechanism for registering a New Device and recovering the User account.A Trusted Circle protocol may use Trustee Lists containing ULIDs ofUsers who are designated as Trustees to send their votes confirming theidentity of a User requiring addition of a New Device to their Userrecord.

Addition of a Trustee list protocol may be implemented in two phases.During the first phase, a User 140 creates a list and the system sendsout notifications to Trustees inviting them to join the list. FIG. 18illustrates such a process. In step 1800, a User 140 configures aTrusted List on a Registered Device 145, and sends a request to add atrustee list (“AddTrusteeListReq”) to TD 100. The AddTrusteeListReqincludes the User's ULID, Live Scan, encrypted hash of Live Scan, DeviceID, Trustee List, and Device public key. In step 1805, TD 100 runs aValidation of User Request protocol and Authentication protocol, asdescribed elsewhere herein. In step 1810, TD 100 forwards the datareceived by it in step 1800 to a smart contract 115A on UL 115. Thesmart contract on UL 115 creates a Trustee List attribute, setting thestatus field of each Trustee to PENDING. The smart contract 115A on UL115 further appends the Trustee List attribute to the User Record. Instep 1815, TD 100 sends notifications to the Trustees designated in step1800, attaching the User's ULID to an invitation to join the TrusteeList.

During a second phase, each of the Trustees will respond signaling theiracceptance (or refusal) of the invitation to join the User's new TrusteeList. FIG. 19 illustrates such a process. In step 1900, an invitedTrustee responds to the invitation of step 1815, by producing a LiveScan and sending to TD 100: a “Confirm Trustee Acceptance” request withthe Trustee's ULID, Live Scan, encrypted hash of Live Scan, Device ID,ULID of Trustee List creator, and device public key. In step 1905, TD100 performs Validation of User Request and Authentication protocols forinformation received from the Trustee, as described elsewhere herein. Instep 1910, TD 100 forwards data received in step 1900 to a smartcontract 115A on UL 115. The smart contract looks up a record belongingto the Trustee List owner and changes the status of the Trustee whoresponded in step 1900, from PENDING to CONFIRMED.

Trusted Circle Recovery Protocol

A Trusted Circle recovery protocol may run in two phases. FIG. 20illustrates a process that may be implemented in a first phase. In step2000, a User 140 initiates the Trusted Circle recovery by installing anapplication on a new PED 145 (i.e., a New Device) and during, e.g., aninitial configuration, select an option to initiate Trusted Circlerecovery. To be able to use this option, User 140 must remember thealphanumeric string that was used to create ULID. Preferably, thisstring is something unique and easy to remember, such as an emailaddress. User 140 may also enter a text-based message to Trustees, suchas “This is Joe on a new phone. I lost my old phone. Please, confirmthat you know me.” User 140 produces a Live Scan from the New Device,and sends a Trusted Circle Recovery Request to TD 100, containing theULID, Live Scan, encrypted hash of Live Scan, message to Trustees, andNew Device public key.

In step 2005, TD 100 runs Validation of User Request and Authenticationprotocols, as described elsewhere herein. In step 2010, TD 100 forwardsdata received by it in step 2000 to a smart contract 115A on UL 115;smart contract 115A in turn adds the New Device to the list ofRegistered Devices and changes the User Record status to RECOVERY. Instep 2015, using data from the User record retrieved in step 2005, TD100 sends notifications to Trustees, attaching the requesting User'sULID and message to Trustees.

A second phase of Trusted Circle recovery is illustrated in FIG. 21 ,whereby each of the Trustees will respond to the notification by votingfor the User whose record access is being recovered. A Trustee hasreceived an invitation sent by TD 100 in step 2015. In step 2100, theTrustee produces a Live Scan and sends a request to Confirm UserRecovery, which includes the Trustee's ULID, the Trustee's Live Scan, anencrypted hash of the Trustee's Live Scan, the Device ID, a ULID of theUser being recovered, and the device public key. In step 2105, TD 100runs the Validation of User Request and Authentication protocols, asdescribed elsewhere herein. In step 2110, TD 100 forwards data receivedin step 2100 to smart contract 115A on UL 115. Smart contract 115A looksup a record of the User being recovered and marks all instances of theresponding Trustee in the Record's Trusted Lists to VOTED. Every time anew vote comes in, a smart contract 115A on UL 115 checks if a minimumvote count condition in any one of the Trustee Lists has been met. If ithas, voting is complete; all Trustees are reset to ACTIVE; and the Userrecord Status changes to ACTIVE. The User can now use the New Device.

For security reasons, Trustees may not be provided with access to thepublic keys of Provider Accounts that would be required to decryptProvider Account descriptions. In such embodiments, when a User with oneor several Provider Accounts recovers his or her Record using theTrusted Circle protocol, the New Device will not be able to display theTrusted Account titles that would be shown during a Provider Accountremoval protocol. This inconvenience can be resolved by, e.g.,contacting Providers and asking them to reset their registration tosupport the User's New Device. This restriction may be implementedintentionally, as it may be undesirable for Trustees from a TrustedCircle List to be able to read contents of the Provider Accountsconfigured in the record of the Trustee List creator.

Enhanced Security of Stored Biometric Samples

In some embodiments, it may be desirable to enable modification ofstored Templates while preserving UL record ownership. For example,biometric data is sensitive and often considered to be irreplaceable. Inmodern biometric authentication systems, templates and live scans arealmost always encrypted when transferred from clients to servers; andtemplates are stored separately from their decryption keys on the serverside. This addresses the concern of data security during transportationand storage. However, during matching, templates and live scans stillneed to decrypted back to their original formats to be matched. If amatching node is compromised or if matching is performed on a publicnetwork, it is possible that a hacker can steal the original template.If this happens, a hacker can create a fake live scan by modifying thetemplate in an insignificant way to spoof the matching algorithm. Sincea user's biometric information does not change, once an originaltemplate is stolen, it will not be safe for the user to use the samebiometrics anymore.

To address this issue, a technique may be implemented that allows a userto revoke and replace biometric templates. Such a technique may be basedon scrambling biometric templates and live scans and matching thescrambled pairs directly without de-scrambling them.

A template is a mathematical representation of a user's biometricinformation. A matching algorithm takes input of a pair ofrepresentations and computes their similarity. Without losinggenerality, hereinbelow are described two commonly used representationsand their associated similarity measurements.

A first type of representation is a feature vector whose similarity iscomputed as a function of dot product. For this example, one may denotethe vectors of template and live scan as A=[a1, a2, a3, . . . , an] andB=[b1, b2, b3, . . . , bn]. The similarity is computed as a function ofC=sum(a1*b1, a2*b2, a3*b3, . . . , an*bn). A can be scrambled bymultiplying a matrix M with the effect of swapping the order of elementsand/or adding different coefficients to different elements. For instanceA′=[k2*a2, k1*a1, kn*an, . . . , k3*a3]. B can be scrambled bymultiplying the inverse of M, M′, B′=[a2/k2, a1/k1, an/kn, . . . ,a3/k3]. Similarity C′=sum(a2*b2, a1*b1, an*bn, . . . , a3*b3)=C.

A second type of representation is a Fourier transform vector. Denotethe vectors of template and live scan as A=[a1*exp(−i*a1),a2*exp(−i*a2), . . . , an*exp(−i*an)] and B=[b1*exp(4*(31),b2*exp(−i*β2), . . . , bn*exp(−i*βn)]. Similarity is computed as afunction of the element-wise product, C=[a1*b1*exp(−i*(α1+β1)),a2*b2*exp(−i*(α2+β2)), . . . , an*bn*exp(−i*(αn+βn))]. Similar to themethod described in the previous section, we can multiply A and B with ascramble vector M and its element-wise inverse vector M′.A′=[k1*a1*exp(−i*α1−i*Ω1), k2*a2*exp(−i*a2−i*Ω2), . . . ,k2*an*exp(−i*αn−i*Ωn)] and B′=[a1/k1*exp(−i*β1+i*Ω1),a2/k2*exp(−i*(32+i*Ω2), . . . , an/kn*exp(−i*βn+i*Ωn)]. The element-wiseproduct C′ will be the same as C. Note that in image processing, Fouriertransform is often computed as 2D matrices instead of 1D vectors.However the above technique is still applicable as the rows of a 2Dmatrix can be concatenated into a single vector. We can then apply thesame element-wise operation above and reshape the result vector backinto a 2D matrix of the original form.

FIG. 22 shows how to apply the scrambling technique to the proposedbiometric authentication system. During enrollment, a client app 2200randomly generates a scramble matrix/vector M (2202) and its inverse(2204) and stores them locally. Upon capturing the biometric template A(2206), the client app calculates a scrambled template A′ by scramblingA using M, and sends the scrambled template A′ to the server 2210. Theserver saves A′ as a template 2212. During authentication, the clientapp 2200 captures a live scan B (2208), scrambles it with M′ and sendsthe scrambled live scan B′ to the server 2210 for matching. The server2210 fetches A′ and matches it with B′. The result 2214 will be the sameas matching the unscrambled A and B.

Scramble matrix/vector M is irreversible, i.e., one cannot derive theoriginal template and live scan A and B from their scrambledrepresentations A′ and B′ without knowing M and M′. Since M is only usedto scramble the template and can be discarded afterwards, and M′ is onlystored in an encrypted format and can only be recovered by registereddevices using their own private keys, and A′ and B′ are matched withoutde-scrambling on the server side, even when a server node iscompromised, the hacker can only get access to A′ and B′ but will not beable to recover A and B. Thus, the original biometric sample and livescan remain secure. After such a hack is detected, the user can simplyrevoke the enrolled template A′, generate a new pair of M and M′, thenre-enroll. The hacker will not be able to spoof the system by resendingslightly modified version of A′ or B′ as the new template is scrambledusing a completely different matrix/vector. Since M and M′ are randomlygenerated, there are infinite number of pairs. So the user can revokebiometric templates as many times as he/she wants to.

In one embodiment, User 140 can create a separate UL record for eachregistered device. In this configuration, M′ can be stored locally inthe registered device. In other embodiments, a UL record is associatedwith multiple registered devices. To implement this approach, a M′ fieldwill be stored in an encrypted format as a part of a UL record. Thetechnique used to store it will be analogous to the Public KeyTranslation Table. Each registered device will be able to load anencrypted M′ and decrypt it with its local private key. FIG. 23illustrates an example of two registered device attributes 2300A and2300B that may be appended to a UL record. Attribute 2300A containsDevice 1 ID 2302A, encryption key 2305A (PuK-Dev1), a field 2310A withM′ encrypted with PuK-Dev1. Similarly, attribute 2300B stores M′ for asecond registered device in field 2310B, along with Device 2 ID 2302Band encryption key 2305B (PuK-Dev2).

To support this enhancement, most protocols will require a minormodification wherein before submitting a Live Scan, the User 140 willobtain a copy of the encrypted M′ from UL 115 via TD 100. UL 115 may bequeried for encrypted M′ in the same manner as described elsewhereherein.

Proving Authenticity of Matching Results by Inserting Test Tasks

While the consensus protocol over a decentralized framework is usuallysufficient to guarantee the authenticity of a matching result, tofurther enhance security, an additional technique can be applied toverify whether a processing node faithfully reported the authenticmatching result. This can be particularly useful when matching isperformed over a public network or when the consensus protocol onlyrequires votes from a small number of nodes.

When passing template and live scan pairs to AL 125 for matching, TD 100can insert testing pairs whose matching results are known to TD 100 asshown in FIG. 24 . A and B are two sets of biometric scans that TD 100sends to AL 125, one as templates and the other as live scans. Thenotation is abstract. Their elements can be whole biometric scans orsub-pieces. The sets can be sent simultaneously as a single task or canbe sent over time as TD 100 continues to send matching requests to AL125. There are two types of elements. The shaded ones represent testingtemplate and live scan pairs whose matching results are known to TD 100.The others represent normal pairs whose matching results are unknown.Testing pairs can be randomly generated by TD 100 and their results arecomputed by TD 100 using the same matching algorithm that AL 125 uses.Or TD 100 can store previous biometric scans and their matching resultsthat have been verified and use them as future testing data.

By matching the reported and known results of the testing pairs, TD 100can decide whether a node or even the entire ledger has been compromisedwith high confidence. When the result is in the format of a Booleanvalue, n testing pairs can verify the authenticity to the accuracy of1/(2 {circumflex over ( )}n). Or when the result is a floating pointvalue, a single testing pair is usually enough.

While certain embodiments of the invention have been described herein indetail for purposes of clarity and understanding, the foregoingdescription and Figures merely explain and illustrate the presentinvention and the present invention is not limited thereto. It will beappreciated that those skilled in the art, having the present disclosurebefore them, will be able to make modifications and variations to thatdisclosed herein without departing from the scope of the invention orappended claims.

The invention claimed is:
 1. A method for biometric authentication of auser utilizing a computer network-enabled user computing deviceconducting a transaction with a provider using a provider computingdevice, comprising: receiving, by a network-connected transactiondirector from the provider computing device, the provider requestcomprising a user record identifier associated with the user and aprovider identifier associated with the provider, wherein thetransaction director comprises a server computer electronicallyconnected via the network to the provider computing device, wherein thetransaction director further comprises a gateway to a first distributeduser ledger (UL) and a second distributed authentication ledger (AL)wherein each ledger comprises a computing system that electronicallycommunicatively links a plurality of computing devices as nodes on ablockchain; querying the UL implemented by the plurality ofnetwork-connected UL nodes, for a user record associated with the userrecord identifier, the user record comprising a biometric template ofthe user, wherein the biometric template was captured and storedimmutably on the UL during the user's registration with the platform;receiving, by the transaction director, from the user computing device,a live scan biometric sample; transmitting, from the transactiondirector to the AL implemented by a plurality of network-connected ALnodes comprising a plurality of processor nodes, an authenticationrequest comprising the biometric template and live scan biometricsample; comparing, by the plurality of AL processor nodes, the biometrictemplate and the live scan biometric sample, to produce a matchingresult, wherein each of the plurality of AL processor nodes comprises aprocessor server executing a biometric matching algorithm; receiving,from the AL processor nodes, the matching result comprising a comparisonbetween the biometric template and live scan biometric sample; andstoring immutably, within the AL by the AL nodes, an authenticationtransaction record comprising the matching result, a hash of thebiometric template, and a hash of the live scan biometric sample.
 2. Themethod of claim 1, wherein the processor nodes comprise a computecluster formed from a plurality of processor nodes, and wherein thematching result is determined by the compute cluster according toconsensus rules.
 3. The method of claim 1, further comprising storing,by said one or more AL processor nodes, an authentication transactionrecord comprising the encrypted biometric template and the encryptedlive scan biometric sample.
 4. The method of claim 1, in which the stepof querying a distributed UL comprises querying a UL node attached tothe transaction director.
 5. The method of claim 1, further comprising:transmitting an authentication outcome based on the matching result tothe provider computing device.
 6. The method of claim 5, wherein thetransaction director is a first transaction director, furthercomprising: verifying operation of the first transaction director by aprovider, by: transmitting, by the provider computing device, to asecond transaction director, a request to read back the matching resultfrom the AL; receiving a matching result from the second transactiondirector; and determining whether the matching result from the secondtransaction director matches the authentication outcome from the firsttransaction director.
 7. The method of claim 1, wherein the usercomputing device is a personal electronic device.
 8. The method of claim1, wherein the user computing device is a trusted shared device.
 9. Themethod of claim 8, in which the trusted shared device is a bankautomated teller machine.
 10. The method of claim 1, wherein the step ofquerying a distributed user ledger further comprises determining whetherthe provider is previously authorized by the user via biometricauthentication to access the user record.
 11. The method of claim 10,wherein the step of determining whether the provider is previouslyauthorized comprises comparing a public key received within the providerrequest to a hash of a provider public key stored within the userrecord.
 12. The method of claim 1, in which the step of receiving a livescan biometric sample further comprises verifying that the usercomputing device is previously authorized by the user to provide a livescan.
 13. The method of claim 1, in which the step of receiving aprovider request further comprises verifying that the provider ispreviously authorized by the user to request authentication of the user.14. The method of claim 1, in which the biometric template comprisesuser original biometric template previously scrambled by a firstscrambling matrix; and the step of receiving a live scan biometricsample comprises receiving an original biometric live scan from the userscrambled by a second scrambling matrix; whereby the first scramblingmatrix and the second scrambling matrix are selected such that thematching result of the user original biometric template previouslyscrambled by a first scrambling matrix and the original biometric livescan from the user scrambled by a second scrambling matrix is the sameas the matching result of the original biometric template and theoriginal biometric live scan.
 15. The method of claim 14 wherein thefirst and second scrambling matrix are both stored in the user deviceand unknown to the AL, transaction director and UL.
 16. The method ofclaim 15, further comprising: regenerating, by the user, a new pair ofscrambling matrices; revoking the biometric template from the UL; andreplacing the biometric template within the user record with a newbiometric template that is scrambled by one of the new scramblingmatrices.
 17. An apparatus for biometric authentication of a user via adigital communications network, comprising: a plurality of computernetwork-connected user ledger node computers communicatingelectronically as nodes on a blockchain to implement a distributed userledger (UL), the UL comprising a user record immutably storing anencrypted biometric template associated with the user, wherein thebiometric template was captured and stored immutably on the UL duringthe user's registration with a platform; a plurality of computernetwork-connected authentication ledger node computers communicatingelectronically as nodes on a blockchain to implement a distributedauthentication ledger (AL), the AL node computers comprising processorcomputers implementing one or more biometric matching algorithms forcomparing the biometric template of a user with a live scan biometricsample; and a computer network-connected transaction director comprisinga computer with an attached UL node and an attached AL node, thetransaction director comprising a computer electronically connected viathe network to a provider computing device, the transaction directorbeing configured to retrieve a biometric template associated with a userfrom the UL, and forward the biometric template with a live scanbiometric sample received from the user at the time of authentication toa compute cluster comprising one or more AL processor computers forcomparison of the live scan biometric sample to the biometric template,the transaction director further receiving a matching result from theone or more AL processor computers; wherein the AL node computers arefurther configured to store within an immutable distributed AL, atransaction record comprising a hash of the biometric template, a hashof the live scan biometric sample, and the matching result.
 18. Theapparatus of claim 17, wherein the AL processor computers within thecompute cluster are configured to store a transaction record comprisingthe biometric template and the live scan biometric sample.
 19. Theapparatus of claim 17, in which plurality of network-connected userledger node computers are configured to implement a smart contractinvoked by the transaction director to modify one or more records withinthe UL.
 20. The apparatus of claim 17, wherein the transaction directorfurther comprises a web interface for programmatic network-basedcommunications with a user computing device and a provider computingdevice.
 21. The apparatus of claim 17, further comprising a plurality oftransaction directors; wherein the provider may verify a biometricauthentication result sent from one transaction director by requestingthat a different transaction director read back an authentication resultfrom the AL.
 22. The apparatus of claim 17, in which the transactiondirector is stateless relative to the AL and the UL.
 23. The apparatusof claim 17, in which the user record further comprises one or moreregistered device attributes, each identifying a computing deviceauthorized to produce a live scan biometric sample for a particularuser.
 24. The apparatus of claim 23, in which the registered deviceattributes each comprise a hash of a hardware and/or software identifieruniquely associated with a registered device, and a public keycorresponding to a private key stored locally on the registered device.25. The apparatus of claim 17, in which the user record furthercomprises one or more provider account attributes, each provider accountattribute identifying a provider authorized to authenticate transactionswith the user.
 26. The apparatus of claim 25, in which each provideraccount attribute comprises a unique provider identifier, a providerdescriptor, and a public key translation table.